1. Field of the Invention
The present invention relates to an apparatus for performing energy transfer among a plurality of battery devices interconnected in series and carried on an electric car or a hybrid car and thereby equalizing each voltage across each of the battery devices interconnected in series.
2. Description of the Related Art
The related art in this field is disclosed, for example, in Japanese Laid-Open Patent Publication No. Hei 11-176483 and U.S. Pat. No. 5,003,244. In the configuration of the former patent as shown in FIG. 7, the output voltages E1 to En of a plurality of battery devices 1-1 to 1-n are interconnected in series. For the purpose of the balance correction of the output voltages of the battery devices, a switching transistor 2 connected to a primary coil Np in series is turned ON and OFF in response to the output voltages. A converter is composed of a plurality of secondary coils Ns each corresponding to each of the battery devices and wound on a common transformer core with the primary coil. The connection thereof is configured such that the secondary output of the converter charges each battery device. When the switching transistor 2 is periodically turned ON and OFF, a voltage depending on the turn number ratio is generated in each secondary coil Ns. Since the secondary coils are wound on the common core, the induced charging current concentrates in a battery device having the lowest voltage among the battery devices, whereby the battery devices are equalized in voltage.
In this former circuit, in addition to that the switching transistor is simply turned ON and OFF, the current Ip flowing in the primary coil Np is controlled depending on the load current Io.
Further, in the configuration of the latter patent as shown in FIG. 8, the output voltages of a plurality of battery devices 25, 26, 27, 28 are connected in series. For the purpose of the balance correction of the output voltages of the battery devices, a switching transistor 34 connected to a primary coil 16 in series is turned ON and OFF in response to the input from a power supply 30. A converter 14 is composed of a plurality of secondary coils 21, 22, 23, 24 each corresponding to each of the battery devices and wound on a transformer core 18 common to the primary coil 16. The connection thereof is configured such that the secondary output of the converter 14 charges each battery device. When the switching transistor 34 is periodically turned ON and OFF, a voltage depending on the turn number ratio is generated in each secondary coil. Since the secondary coils are wound on the common core, the induced charging current concentrates in a battery device having the lowest voltage among the battery devices, whereby the battery devices are equalized in voltage.
There has been the following problems in such above-mentioned related art apparatuses for equalizing the voltages across each of a plurality of energy storage device (battery devices) interconnected in series by means of the switching of a converter.
(a) In each above-mentioned related art apparatus, the magnetizing force is one directional in the transformer core for the ON and OFF duration of the switching device (transistor) Accordingly, the range of the change in magnetic flux density of the core is small, and hence the utilization of the core is less efficient. The lower efficiency in core utilization implies the necessity of a larger cross section in the core for a specific output power, thereby causing the problems of a larger apparatus and a higher cost.
Further, the switching ON and OFF of the switching device for the voltage equalizing causes a problem that electric charge stored in the capacitance existing between the terminals of the switching device for the OFF duration of the switching device is discharged by the next ON operation thereby to cause a power loss and a noise due to the short-circuit current.
(b) In each above-mentioned related art apparatus, energy stored in the transformer for the ON duration of the switching device is discharged for the next OFF duration of the switching device, thereby charging a battery device having the lowest voltage among the battery devices thereby to equalize the output voltages of the battery devices. Accordingly, the amount of equalizing energy is only the amount of energy stored for the ON duration of the switching device. Therefore, in order to increase the equalizing action, a larger switching device is necessary for increasing the equalizing current. However, this larger switching device causes a larger apparatus and hence a higher cost, as is the above-mentioned case (a). Further, since each battery device has an internal resistance, the higher current from the switching device causes a larger voltage drop across the internal resistance, thereby increasing apparent output voltage of the battery device in charging. This causes a problem of reducing the precision of output voltage equalizing.
In addition to resolving the above-mentioned problems, earnestly desired are short-time equalization of the output voltages of the battery devices, reduction of energy loss after the equalization operation, and setting of the voltage at an arbitrary value after the equalization.
An object of the present invention is to resolve the above-mentioned problems (a) and (b) thereby to provide a voltage equalizing apparatus having a high efficiency and a high precision of equalizing and being of a small size. Further, an object of the present invention is to provide a voltage equalizing apparatus capable of equalizing to a desired voltage in a short time, reducing the energy loss after the completion of equalization, and setting the voltage after the equalization to be an arbitrary value.
An aspect of the invention for resolving the above-mentioned problems is a voltage equalizing apparatus for battery devices comprising:
a core;
a plurality of first closed circuits each composed of one of a plurality of first battery devices (1-1 to 1-n) interconnected in series, one of a plurality of secondary windings (4-1 to 4-n) magnetically connected with each other through the core (3), and one of a plurality of first switching devices (2-1 to 2-n); and
a second closed circuit composed of a second battery device (1-m), a primary winding (4-m) magnetically connected with the secondary windings through the core, and a second switching device (2-m);
wherein the first switching devices and the second switching device are alternately turned ON and OFF to equalize the output voltages of the first battery devices;
when the second switching device is turned ON, exciting energy stored in the core is transported to the first battery devices through the first switching devices; and
the first switching devices continue to be turned ON after the transportation of the exciting energy is completed.
According to the present invention,
when the second switching device is turned ON, exciting energy stored in the core is transported to the first battery devices through the first switching devices, and
the first switching devices continue to be turned ON after the transportation of the exciting energy is completed.
In another configuration, a detector for detecting the variation in the output voltages of the first battery devices (1-1 to 1-n) is provided, whereby in case of a large variation, the ON duration of the second switching device (2-m) and/or the first switching devices (2-1 to 2-n) is extended.
In another configuration, in case of a small variation in the output voltages of the first battery devices, the ON/OFF operation of the first switching devices and the second switching device is stopped, and/or the ON duration of the first switching devices and the second switching device is extremely shortened. This avoids power loss and noise due to unnecessary voltage equalizing operation in case of the small variation in the output voltages.
In another configuration, in case that the variation in the output voltages of the first battery devices becomes smaller than a predetermined value, the ON duration of the first switching devices and/or the second switching device is shortened for the reduction of power consumption for the equalizing. By virtue of this, the precision increases in equalizing the terminal voltages of the battery devices.
In another configuration, in case that a current greater than or equal to a predetermined value flows through the first battery devices, the ON/OFF operation of the first switching devices and the second switching device is stopped, and/or the ON duration of the first switching devices and the second switching device is extremely shortened. By virtue of this, the voltage equalizing operation is substantially stopped when the cell voltage detection of each battery device is affected by a voltage drop generated across the internal resistance of the battery device by a high current flowing through the first battery devices.
In another configuration, during the charge from an external power supply and the discharge to an external load by the first battery devices, the ON/OFF operation of the first switching devices and the second switching device is stopped, and/or the ON duration of the first switching devices and the second switching device is extremely shortened. By virtue of this, the voltage equalizing operation is stopped, even without current detection, automatically in response to the operation of a switch (S11) for switching the charge and discharge modes.
In another configuration, when the first switching devices and the second switching device are alternately turned ON and OFF, there is a pause in an interval from the switching-OFF of the first switching devices to the switching-ON of the second switching device and in an interval from the switching-OFF of the second switching device to the switching-ON of the first switching devices. By virtue of this, each switching device can be turned ON under the condition of substantially no electric charge in the capacitance component between the terminals of the switching device in question (zero-volt switching)
Another aspect of the invention is an apparatus for equalizing circuit voltages, comprising:
a plurality of circuits, wherein in each circuit, each of a plurality of closed circuits is constituted of each of a plurality of first battery devices interconnected in series, each of a plurality of secondary windings magnetically coupled with each other, and each of a plurality of first switching devices, and wherein each circuit comprises a transformer having at least a circuit equalizing winding magnetically coupled with the secondary windings in common;
wherein the circuit equalizing windings each provided in each circuit are interconnected in parallel, wherein at least one of the circuits is provided with an exciting winding magnetically coupled with the secondary windings involved in the circuit in question, wherein a closed circuit is constituted by the serial connection of the exciting winding, a second battery device, and a second switching device, and
wherein when the second switching device is turned ON, exciting energy stored in the core is transported to the first battery devices through the first switching devices, and
the first switching devices continue to be turned ON after the transportation of the exciting energy is completed.
Accordingly, there is a further effect that a necessary output voltage can be obtained by an appropriate combination of single circuits.
In another configuration alternative to claim 9, when the first switching device is turned ON, exciting energy stored in the core is transported to the second switching device through the second switching device, and
the second switching device continues to be turned ON after the transportation of the exciting energy is completed.
By virtue of this, voltage equalizing operation similar to that within each single circuit is achieved also among the circuits, whereby overall voltage equalizing operation is obtained.
The combined use of the exciting winding and the circuit equalizing winding permits a miniaturization of the apparatus.
Another aspect of the invention is a voltage equalizing apparatus for battery devices comprising:
a core;
a plurality of first closed circuits each composed of one of a plurality of first battery devices interconnected in series, one of a plurality of secondary windings magnetically connected with each other through the core, and one of a plurality of first switching devices;
a second closed circuit composed of a second battery device, a primary winding magnetically connected with the secondary windings through the core, and a second switching device; and
a controller for outputting a control signal for causing the second switching device and the first switching devices to be alternately turned ON and OFF, thereby causing the energy transportation between the second battery device and each of the first battery devices, and thereby equalizing the voltages of the first battery devices;
wherein the controller sets the ON-duration ratio between the ON duration of the second switching device and the ON duration of the first switching devices so that the voltages of the first battery devices become a predetermined voltage.
By virtue of this, voltage equalization is carried out and a predetermined voltage is obtained.
Another aspect of the invention is a voltage equalizing apparatus for battery devices comprising:
a core;
a plurality of first closed circuits each composed of one of a plurality of first battery devices interconnected in series, one of a plurality of secondary windings magnetically connected with each other through the core, and one of a plurality of first switching devices;
a second closed circuit composed of a second battery device, a primary winding magnetically connected with the secondary windings through the core, and a second switching device; and
a controller for outputting a control signal for causing the second switching device and the first switching devices to be alternately turned ON and OFF, thereby causing the energy transportation between the second battery device and each of the first battery devices, and thereby equalizing the voltages of the first battery devices;
wherein the controller sets the ON-duration ratio between the ON duration of the second switching device and the ON duration of the first switching devices so that the voltages of the first battery devices exceed a predetermined voltage, and wherein before the voltages of the first battery devices exceed the predetermined voltage, the controller resets the ON-duration ratio so that the voltages of the first battery devices become the predetermined voltage.
By virtue of this, the time necessary for the energy transportation from the second battery device to each of the first battery devices is further reduced.
In another configuration, the controller sets the frequency which is the reciprocal of the sum duration of the ON duration of the second switching device and the ON duration of the first switching devices, to be a frequency lower than a normal value, thereby increasing the amount of energy transported between the second battery device and each of the first battery device in a unit time so that the voltages of the first battery devices become the predetermined voltage in a short time. By virtue of this, the voltages of the first battery devices are set to the predetermined voltage in a shorter time.
In another configuration, when the transportation of a predetermined amount of energy between the second battery device and each of the first battery devices is completed and when the voltages of the first battery devices have become approximately the predetermined voltage, the controller sets the frequency which is the reciprocal of the sum duration of the ON duration of the second switching device and the ON duration of the first switching devices, to be a frequency higher than the normal value. This permits reduction of the circulation energy after the equalization is completed, and hence the energy loss is reduced.
In another configuration, when the transportation of a predetermined amount of energy between the second battery device and each of the first battery devices is completed and when the voltages of the first battery devices have become approximately the predetermined voltage, the controller turns OFF the second switching device and the first switching devices. This permits reduction of energy loss.
In another configuration, a third switching device and a third battery device are further provided in the second closed circuit composed of, the second battery device, the primary winding, and the second switching device,
a closed circuit is formed by the second battery device, the third switching device, and the third battery device,
a closed circuit is formed by the primary winding, the second switching device, and the third battery device, and
when the transportation of a predetermined amount of energy between the second battery device and each of the first battery devices is completed, the controller turns OFF the third switching device and causes the second switching device and the first switching devices to continue, thereby causing the equalization of the voltages of the first battery devices to continue.
When almost all of the energy to be transported has been completed, equalization is carried out efficiently in case that only a small amount of energy is transported between the primary winding and the secondary windings. Accordingly, energy loss is reduced when the third switching device is turned OFF and when the third battery device having an energy capacity smaller than that of the second battery device is used for equalization.
Another aspect of the invention is a voltage equalizing apparatus for battery devices comprising:
a core;
a plurality of first closed circuits each composed of one of a plurality of first battery devices interconnected in series, one of a plurality of secondary windings magnetically connected with each other through the core, and one of a plurality of first switching devices;
a plurality of second closed circuits each composed of one of a plurality of second battery devices interconnected in series, one of a plurality of primary windings magnetically connected with the secondary windings through the core, and one of a plurality of second switching devices; and
a controller for outputting a control signal for causing the second switching devices and the first switching devices to be alternately turned ON and OFF, thereby causing the energy transportation between each of the second battery devices and each of the first battery devices, and thereby equalizing the voltages of the second battery devices and/or the first battery devices;
wherein the controller sets the ON-duration ratio between the ON duration of the second switching devices and the ON duration of the first switching devices so that the voltages of the second battery devices or the first battery devices become a predetermined voltage.
This permits the two-directional energy transportation and the voltage equalization between each of the second battery devices and each of the first battery devices. This control method further permits a small voltage equalizing apparatus of low noise. Further, when the ON duration is set as described above and the activation of the second switching devices and the first switching devices is controlled, the voltages of the second battery devices and the first battery devices can be set to a predetermined value. Accordingly, equalization is achieved, and a predetermined voltage is obtained.
Another aspect of the invention is a voltage equalizing apparatus for battery devices comprising:
a core;
a plurality of first closed circuits each composed of one of a plurality of first battery devices interconnected in series, one of a plurality of secondary windings magnetically connected with each other through the core, and one of a plurality of first switching devices;
a plurality of second closed circuits each composed of one of a plurality of second battery devices interconnected in series, one of a plurality of primary windings magnetically connected with the secondary windings through the core, and one of a plurality of second switching devices; and
a controller for outputting a control signal for causing the second switching devices and the first switching devices to be alternately turned ON and OFF, thereby causing the energy transportation between each of the second battery devices and each of the first battery devices, and thereby equalizing the voltages of the second battery devices and/or the first battery devices;
wherein the controller sets the ON-duration ratio between the ON duration of the second switching devices and the ON duration of the first switching devices so that the voltages of the second battery devices or the first battery devices exceed a predetermined voltage, and wherein before the voltages of the second battery devices or the first battery devices exceed the predetermined voltage, the controller resets the ON-duration ratio so that the voltages of the second battery devices or the first battery devices become the predetermined voltage.
This permits further reduction of the time necessary for the energy transportation from each of the second battery devices to each of the first battery devices or vice versa.
In another configuration, the controller sets the frequency which is the reciprocal of the sum duration of the ON duration of the second switching devices and the ON duration of the first switching devices, to be a low frequency, thereby increasing the amount of energy transported between each of the second battery devices and each of the first battery devices in a unit time so that the voltages of the second battery devices or the first battery devices become the predetermined voltage in a short time. By virtue of this, the voltages of the second battery devices or the first battery devices are equalized to the predetermined voltage in a shorter time.
In another configuration, when the transportation of a predetermined amount of energy between each of the second battery devices and each of the first battery devices is completed and when the voltages of the second battery devices or the first battery devices have become approximately the predetermined voltage, the controller sets the frequency which is the reciprocal of the sum duration of the ON duration of the second switching devices and the ON duration of the first switching devices, to be a high frequency. This permits reduction of the circulation energy after the equalization is completed, and hence the energy loss is reduced.
In another configuration, when the transportation of a predetermined amount of energy between each of the second battery devices and each of the first battery devices is completed and when the voltages of the second battery devices or the first battery devices have become approximately the predetermined voltage, the controller turns OFF the second switching devices and the first switching devices. By virtue of this, both the second switching devices and the first switching devices are maintained to be OFF simultaneously, whereby energy loss is reduced.